1. Technical Field
This disclosure relates to an image-forming apparatus, and more particularly, to an image-forming apparatus that is equipped with a recording head for ejecting ink droplets and a transport belt for transporting sheets of recording media onto which the ink droplets are ejected to form an image.
2. Discussion of the Background
As an image-forming apparatus, such as a printer, a facsimile machine, a plotter, or a multifunction machine including at least two of these functions, a liquid-ejecting image-forming apparatus such as an inkjet recording device that uses a recording head for ejecting ink droplets is known.
There are two types of the liquid-ejecting image-forming apparatuses. A serial-type image-forming apparatus forms images using a recording head that ejects ink droplets while moving in a main scanning direction. By contrast, a line-type image-forming apparatus forms images using a recording head that remains stationary while ejecting ink droplets.
In either case, the liquid-ejecting image-forming apparatus forms images by ejecting the ink droplets from the recording head onto a sheet of recording media while the sheet is being transported. Therefore, the transport characteristics of the image-forming apparatus profoundly affect imaging performance.
Such a liquid-ejecting image-forming apparatus is equipped with a maintenance-recovery mechanism that performs maintenance and recovery, in other words cleaning, of a recording head for ejecting the ink droplets.
The maintenance-recovery mechanism for the recording head generally includes a moisturizing cap, a suction cap, wiper members, wiper cleaners, and an idle ejection receiver.
The moisturizing cap seals a nozzle surface of the recording head so as to keep the nozzle surface moist and prevent it from drying out.
The suction cap is connected to a suction mechanism, such as a suction pump, that suctions and discharges ink the viscosity of which has increased from the nozzle. It is to be noted that the moisturizing cap may serve as the suction cap as well.
The wiping members (wiper, wiper blade) wipe and remove any ink adhering to the nozzle surface. The wiper cleaner cleans the wiper. The idle ejection receiver receives the ink droplets that are ejected in an idle ejection that is a clearing operation and do not contribute to forming images.
Such cleaning is performed in various ways. Thus, for example, in one known liquid-ejecting image-forming apparatus, a head unit containing the recording head pivots to an upright position, after which the head unit slides to a position facing a maintenance-recovery unit so as to be cleaned.
In another known liquid-ejecting image-forming apparatus, even during printing, in order to cap a head unit that is not in use, a maintenance-recovery unit is disposed downstream from the head unit in a direction in which a recording media is transported.
Additionally, a known liquid-ejecting image-forming apparatus includes a transport unit to transport sheets using a transport belt, an image-recording unit such as a recording head that is equipped with several ink-ejecting ports aligned in the same direction as a direction in which the transport unit transports the sheets, and a release mechanism that switches the transport unit between an image-recording state and a release state to facilitate removal of a jammed sheet.
In the image-recording state, the transport unit can transport the sheets close to the ink ejecting ports. In the release state, the transport unit is disengaged from all ink releasing ports and is almost parallel to or inclined with respect to the image-recording unit.
As a separate matter, it is to be noted that when a liquid-ejecting image-forming apparatus forms images, a gap between a reading head and a surface of the sheet must be kept constant, that is, maintained at a predetermined or given distance. Therefore, a distance between the recording head and a surface of the transport belt is generally adjusted according to a thickness of a sheet of recording media used in an image forming operation.
Thus, in another known liquid-ejecting image-forming apparatus, the head unit is mounted on a sliding device that includes a vertically moving mechanism, and a surface position of a recording media is detected so that the gap is adjusted to a predetermined or given distance.
As an additional complication, in the above-described image-forming apparatus, line-type recording head units are widely used in order to improve a printing speed. A known line-type recording head unit includes nozzle lines each of which extends in an entire width of the sheet. In another known line-type recording head unit, each nozzle line is formed by multiple recording heads arranged to extend in an entire width of the sheet.
In order to maintain and recover such line-type recording heads, generally, configurations like those described below are adopted.
In one configuration, both multiple line-type recording heads and maintenance-recovery mechanisms (maintenance mechanisms or cleaning mechanisms) are arranged in alternating rows in a direction in which the sheet is transported, and the line-type recording heads and maintenance-recovery mechanisms move repeatedly relative to each other in both horizontally and vertically to carry out the cleaning of the recording heads.
However, such a configuration is relatively complicated. Moreover, in the above-described configuration, the distance between the multiple line type recording heads is longer, and accordingly, color deviation, which means that the different color ink droplets are not properly aligned in a multicolor image on the sheet, is likely to occur.
In another configuration, the maintenance-recovery mechanism is located in the shoulder of sheet transport route, which is out of the sheet transport route in a direction orthogonal to the sheet transport route, and the line type recording head rotates to the maintenance-recover mechanism.
However, in this configuration, a depth of the image-forming apparatus is relatively long.